The synthesis of the organometallic compound ferrocene in the early nineteen fifties has sparked great interest in construction and use of these compounds. This is especially so in terms of snythesis and properties of stacked columns of organometallics. See also Werner, Ang. Chemie Int. Ed. 16, 1-64 (1977); Lee, M.-T., et al., Organometallics 3, 539,547 (1985).
Some of the monomeric and polymeric organometallics possess unusual properties useful in electrical conduction or catalysis. For example, ferrocene (R.sup.1 MR.sup.1) where R.sup.1 =the cyclopentadienyl ring and M=Fe, and ferrocene polymer have been used as anti-knock agents in gasolines, as combustion catalysts in rocket propellants, and as reversible electronic conductors. See U.S. Pat. No. 3,968,126 (1976) (combustion catalyst in rocket propellants); U.S. Pat. No. 4,025,541 (1977) (electrical conducting compounds); U.S. Pat. No. 3,807,213 (binder compositions for rocket propellants).
Ferrocene itself was first prepared utilizing the reaction of cyclopentadienylmagnesium bromide with FeCl.sub.3 in diethyl ether-benzene solution.
Recent synthetic methods of producing other organometallic compounds rely on the use of metal-promoted coupling reactions of organic halides with organometallic derivatives. See E. Negishi, Pure Appl. Chem. 53, 2333 (1981); D. Milstein and J. K. Stille, H. Am. Chem. Soc. 101, 4981 (1979); Felkin, H. and G. Swierczewski, Tetrahedron 31, 2735-2748 (1975); Tamao, K. et al., Bull. Chem. Soc. Japan 49, 1958-1969 (1976). This includes the synthesis of metallocenes by the coupling of metallated ferocenes with halo-aromatics. Lee, M. T. et al., Organometallics 3, 539 (1985). In this latter procedure, however, the polymers can only be derived from monomeric metallocenes capable of being converted into their dichlorozinc derivatives, as exemplified by the following reaction. ##STR1##
Moreover, attempts to prepare polymers from certain dianionic cyclopentadienides derived from as and S-indacenes, fulvalene, bis(cyclopentadienyl)methane and pantalene have generally failed. See Bell, W. L. et al., Organometallics, 6, 266 (1987); Katz, T. J. et al., J. Am. Chem. Soc., 94, 3281, 6204 (1972), and J. Am. Chem. Soc., 95, 2934 (1973); Katz, T.J. and J. Pesti, J. Am. Chem. Soc., 104, 346 (1982). This is likely due to entropic factors, which favor dimer or trimer formation over chain growth polymerization processes.